let file = System.IO.File.Create("BigFile.dat")
let buffer = Array.zeroCreate<byte> 100000000
let asyncWrite = Async.FromBeginEnd(buffer, 0, 100000000, file.BeginWrite, file.EndWrite)
let asyncRead = Async.FromBeginEnd(buffer, 0, 100000000, file.BeginRead, file.EndRead)

Async.RunSynchronously(asyncWrite)
printfn "Wrote file."
Async.RunSynchronously(asyncRead) |> ignore
printfn "Read file."